Survival of the Sickest
"Parasites hunt us for our iron; cancer cells thrive on our iron. Finding, controlling and using iron is the game of life. For bacteria, fungi, and protozoa, human blood and tissue are an iron gold mine. Add too much iron to the human system and you may just be loading up the buffet table." (Page 6)
Not only does the human body need iron to survive but all other living organisms need it too. Iron is an essential element in an organisms diet and occurs naturally in plant and animal life. Iron is needed for the well being of the organism as well as to provide energy. It is an element in the hemoglobin molecule which carries oxygen in red blood cells. However, as stated in the quote from the book, not only do humans and plants need iron but also, bacteria, fungi and protozoa. This relates directly to a topic of discussion that came up quite a bit in our studies this year, symbiotic relationships. There are seven different types of symbiotic relationships that occur between two individuals of different species. The first relationship is called cooperation where both individuals benefit but are independant of one another. An example of this would be with oxtail birds and gnus. "The gnu is covered in with tiny parasites that provide the bird with food and in return, the oxtail bird keeps the gnu free of parasites." (1) Mutualism is another form of a symbiotic relationship. In this case both individuals benefit but they are dependant upon eachother. An example of this could be the bacteria that resides in the human stomach. In other symbiotic relationships both individuals do not always benefit. In commensalism one benefits and the other in unaffected. However, in amensalism one individual is harmed while the other is unaffected. An example of this would be spanish moss that grows on trees. "Spanish moss grows on trees and chokes out virtually all light going to the tree. While the Spanish moss remains unaffected, the tree does not receive enough light to perform an adequate amount of photosynthesis to survive."(1) This relationship is much different than the one that is talked about in this excerpt. Parasitic symbiosis is when one individual is harmed and the other benefits. It could be as simply as a leech sucking the blood out of a human. These bacteria, parasites, fungi and protozoa mentioned all thrive off of iron, which essentially is human blood and tissue. In most cases this would not be a relationship that would benefit both the human and the bacteria. Connecting this idea of symbiosis to a major theme in biology would definitely have to be interdependance in nature.
Interdependance in nature basically states that every organism on earth depends on another one in nature to survive. Without plants and trees that produce oxygen into the air, humans would not be able to breathe. Without plants, animals that are not carnivores would go hungry. Everything depends on something else is order to survive. Even cancer cells use the iron in our blood to survive and reproduce. In this excerpt it seems as though iron is basically the most sought out nutrient and element in life. Because not only do we depend on it but every other organism depends on it too. A question to throw out there would be, what if iron did not exist? What would be composed in the make up of our red blood cells? As the excerpt goes on it says something interesting that also pertains to symbiotic relationships that do not benefit both individuals. "Add too much iron to the human system and you may just be loading up the buffet table." As everyone knows, a buffet table does not really benefit the table in any way. The people eating it are supplying their bodies with food and energy so only really affecting them. With too much iron, our bodies have become that table. The bacteria, fungi, protozoa and parasites are just feeding off of any and all iron they can get their mouths on. While looking at this excerpt one may not think these relationships could be harmful however the words, 'parasites' and 'cancer' are usually associated with harmful relationships. As previously mentioned parasitic relationships benefit one and harm the other. Cancer is a whole other topic however something that we discussed throughly in class. It is a rampant disease and cells divide and reproduce very quickly. If iron is a source used to enhance this process, then again loading our body up with iron is probably not a good idea. Iron is an essential element in the body's diet however too much of a good thing can be dangerous.
I think that this excerpt greatly connects with many themes that we have discussed in class throughout the year, especially interdependance in nature. We
discussed symbiotic relationships, positive and negative and how cancer cells will do anything to invade the body's organs and destroy them.I think that the level of difficulty of the reading is comparably low to what we have been reading all year however I would not really expect it to be any different. This book was written for people in general not just "science people."
Post 2
"On the other hand, as much as plants want animals to eat their fruit,they don't want animals to get much closer than that- when creatures start to nibble on their leaves or gnaw at their roots, things can get tricky. So plants have to be able to defend themselves. Just because they're generally immobile doesn't mean they're pushovers." (Page 78)
Just like the human body, plants have defense mechanisms to fight off diseases and unwanted materials that try to break through their cell walls. Whereas humans have nonspecfic and specfic defenese mechanisms, plants have passive and active defenses. A plant's passive defense would correlate with the job of the human skin. "This type of defense response is due to the presence of some structural components or some type of metabolites present in the body of the plant." (1) An example of this would be thorns,cuticle or wax which cannot be digested by predators to the such as fungi or bacteria. However, trees that have tough bark usually stop any bacteria from penetrating the surface and moving into the cells of the tree. The plant also contains secondary metabolites, which could be things such as alkaloids, tannins and phenols which are dangerous and toxic to insects and other pests. Because plants cannot run away from insects and animals that like to feed off of them, as stated in the excerpt they are "generally immobile," they need other things to keep them from being eaten and dying off. The other part of the plant's defense mechanisms is called active defense. Active defense is produced when the plant is exposed to a pathogen, it is a newly developed response inside the plant, it does not exist until the plant is exposed to some bacteria or pathogen. "The plant cell wall is one of the sites where the change due to the defense response can be observed. All changes that happen in the cell wall due to an infection are collectively known as wall apposition."(1) As a pathogen tries to enter the plant, the cell wall gets thicker in order to make the fungi or bacteria penetration impossible. Another active response mechanism is called HR, hypersensitive response. The metabolic activity of the cells around the infected site change, their respiration slows down and they start to accumulate toxic compounds. This creates a uncomfortable enviornment for the pathogen and essentially prevents the growth and spread of the pathogen throughout the plant and to more cells in the plant body. As these cells are exposed to the "new" bacteria they release chemicals called phytoalexins. "Phytoalexins are small molecular weight compounds produced when there is microbial attack or under conditions of stress, which are completely absent in healthy tissue." (1) Phytoalexins are related to memory B cells in the specfic defense mechanisms in the human body. The memory B cells can detect when their is a forgein invader and automatically stores that information. When the disease or pathogen comes in contact with the human again, these cells are released and find the invader and are able to fight off the disease quicker because of their memory of how to fight off the disease from earlier. The difference is that phytoalexins are not present in healthy tissue, memory B cells are however they are most useful at the site of an infection or bacteria that the body has seen before. The diagram below demonstrates the plant defense responses and what happens to the fungal pathogen as it enters the cell and where it goes from there. Other chemicals are shown that are not mentioned above however each of these goes into the process of defense that occurs within a plant when a pathogen tries to penetrate the cell wall.
There are also other things that plants do to help them survive because they cannot move. We discussed many things in class however one that stuck out in my mind was the regulation of the stomata and transpiration within the plant. Just because it is hot, humid and windy out does not mean a plant or tree can get up and find shade until the weather cools off. The regulation of the stomata opening during the day and closing during the night is something they plants do to defend themselves. The stomata are closed at night because photosynthesis can only take place with sunlight, during the day therefore if the stomata were to be open during the night, the plant would be transpiring and losing water for no reason. However, during the day if the plant is becoming dehydrated or if it starts losing alot of water, the stomata will close. This will help prevent the loss of too much water which can also be categorized as a defense mechanism. This excerpt can be connected to one of the major themes in biology which is regulation. Regulation is," Everything from cells to organisms to ecosystems is in a state of dynamic balance that must be controlled by positive or negative feedback mechanisms." (2) Everything in nature must be balanced. It could be the regulation of the stomata opening and closing or from "homeostatic control of cellular and body conditions."(2) The stomata is regulating the gas exchange in and out of the plant as well as keeping the levels of transpiration in tact.
Post #3
" 'Superbugs' spread fear far and wide. Rising deadly infections puzzle experts. Bacteria run wild, defying antibiotics. You've seen the headlines. They've probably frightened you. And it's true-just as we've been evolving to survive disease, all the organisms that cause disease have been evolving right along with us. You've seen how parasites have evolved very specialized abilities to navigate seemingly impossible challenges to survival- like travelling from a sheep to a snail to an ant in order to get to another sheep. And small organisms, because they multiply so rapidly and so frequently, sometimes cycling through hundreds of generations in just days, have one big evolutionary advantage over us- they evolve faster." (116-117)
The big question that has been circling the minds of scientists, researchers and the victims that the bacteria is infecting is, what are the bacteria doing to stay alive that we can't? The answer is right in this quote and I cannot agree more. These organisms are so small and so vicious that they will do anything to keep its "species" alive. It multiples and developes faster than humans can think. Because they are evolving faster they are also changing and mutating more and faster and figuring out ways to beat our strongest and highest levels of antibiotics. In today's society MRSA is a huge problem especially the staphylococcus aureus strain. The strain is a group of bacteria that can cause various disease as a result of infection from different tissues in the body. What is interesting is that the staph bacteria can be found on the skin of 25-30% of adults however it will not do any harm until the skin is broken and an infection breaks out. MRSA is today's "superbug." Not only is it getting harder and harder to treat but because the survival rate of very severe MRSA infections is so low, the disease is surviving and moving on to other victims. In class we not only talked about MRSA and did a lab demonstrating how the bacteria in the noses of some classmates could be resistant to some of the highest antibiotics, such as vancomysin and lyncomysin. I can also connect this quote with Darwin's Theory of Natural Selection. "As many more individuals of each species are born than can possibly survive; and as, consequently, there is a frequently recurring struggle for existence, it follows that any being, if it vary however slightly in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance of surviving, and thus be naturally selected. From the strong principle of inheritance, any selected variety will tend to propagate its new and modified form."(1) This is basically stating that organisms will evolve to better themselves and if they don't their species will die off. Organisms that have certain traits that make them weak, they should be cut off from the world according to the natural selection theory. This theory can connect with the superbug craze because the people that do not aquire this disease or who have some mutation in their bodies that prevent them from dying from diseases, like MRSA, they are the organisms that will move on. They are the organisms that will pass their traits on and then generations after them can beat and survive the superbug. According to the natural selection theory, the people who do contract this "bug" are meant to die because they cannot survive and live through the natural bacteria that is passing through the generations of people today. This image is showing a magnified view of the staph aureus bacteria. This concept of the superbug and the excerpt from the book greatly connects with the theme of Evolution that we have studied all year. Evolution is a gradual process in which something changes into a different and usually more complex or better form.(2) Humans change and have evolved from many animals which started off in the water. When moving to land they needed to make changes in the way they were structured and the way they functioned. This is what ultimately makes up evolution, the process of change and development. Starting at one point and ending at another which is more complex and advanced. Essentially, evolution has created this superbug. Bacteria has manipulated itself into forms that scientists today cannot even control. As humans have evolved, we have acquired more sophisticated and complex things within our bodies that are able to resistant and fight off pathogens and bacteria. However, in the case of the superbug, evolution is a funny thing. The bacteria is changing faster than we are, that is why we are getting beaten by it. This proves that natural selection is not just a theory but real and taking place in today's society. As people die and learn to fight off the disease, we are letting natural selection take its' course and whoever is supposed to die will die and whoever is supposed to live on will survive. It is all in the hands of evolution and who has the genes and the traits to fight off the pathogen and overcome natural selection.
"In April 2003, researchers announced that they had isolated the genetic mutation that causes progeria. The mutation occurs in a gene that is responsible for the production of a protein called lamin A. Normally,lamin A provides structural supports for the nuclear membrane, the package that houses your genes at the core of every cell. Lamin A is like the rods that hold up a tent- the nuclear membrane is organized around it and supported by it. In people who ave progeria, lamin A is defective and cells deteriorate much more rapidly." (page 184)
All genes are responsible for different traits and characteristics of the body. A gene resides at a specific location on the chromosome which is commonly called the gene locus. The place in which a gene is located determines what trait or characteristic it expresses. When looking at this quote, it talks about progeria which is a very rare aging disorder. People usually die in their teens with this disorder and no one has said to live past 30. This is because by the time the individual that posseses this disorder is one and a half years old, their hair starts to fall out and their skin starts to wrinkle. In the book, Survival of the Sickest, it talks about a boy who is 12 years old however has symptoms of one of the oldest people in America. He takes pills to thin his blood, his arteries are hardened and he has arthritis. Usually people with this disorder die in their teens from a heart attack or a stroke. Not only is this the result of a genetic mutation, but the gene on the locus of the chromosome that maintains the steady aging process, would have to be defected in some way. A mutation is, "a permanent change in the DNA sequences that makes up a gene. Mutations range size from a single DNA building block to a large segment of a chromosome."(1) Gene mutations can occur in two different ways, being inherited from a parent or acquiring this mutation during a person's lifetime.Mutations that are passed down from the parents to the children are called hereditary mutations. It is present in every cell throughout the person's body throughout their lifetime. There are mutations that only in occur in the sperm or eggs cells, which are called De novo mutations. These mutations help people understand why a child has a certain disorder however their is no history of that disorder in the child's parents or family. Lastly, there is something called acquired mutations that occur in the DNA of individual cells throughout a person's life. These mutations can be the result of environmental factors such as ultraviolet radiation from the sun. It is important to note however, that these mutations cannot be passed down. The genetic disorder of progeria would be classified, I believe, in the De novo mutation category. Neither parent would have this disease because if they did, they would not live long enough to have a child. Also, this disorder is so rare, only 1 child gets this disease in 8 million births. It would not be possible to have a family history of this because it is not that common. There must be some kind of mutation in the sperm and/or the egg once fertilization takes place. This excerpt connects to what we have learned this year in class because we have specifically talked about chromosomes, genes and traits that will or will not be expressed because of certain factors. We have also discussed mutations and why they occur and what results from a mutations. When I read this excerpt I immediately thought of the karyotype activity where each chromosome was visible and each student was asked to pick out the mutations or the defects and figure out the disease in which the person had. Here is a picture of a karyotype for a person with the progeria disease.
Also, like it says in the quote, this disease is caused by a mutation in the LMNA gene. "The LMNA gene produces the Lamin A protein, which is the structural scaffolding that holds the nucleus together. Researchers now believe that the defective Lamin A protein makes the nucleus unstable. That cellular instability appears to lead to the process of premature aging in Progeria."(2) By just one small change in the certain gene at a certain point along the chromosome, it could drastically affect the future life of that individual. The theme that this connects to is genetics. "Genetics is the branch of biology that deals with heredity, especially the mechanisms of hereditary transmission and the variation of inherited characteristics among similar or related organisms." (3) Personally, I believe that everything must come from someone or somewhere. These mutations must be triggered by something in the parent cell even if the parent cell does not possess the gene or the defect that will cause certain diseases. Everything is based off of genetics, the way we look, the way we talk, and the way we act. Just because there are two parents with brown hair that have a child with blonde hair, does not mean this gene for blonde hair popped up out of nowhere. The topic of recessive and dominant alleles and genes will then come into play. However, according to the research done on the aging disease, progeria, it does come from nowhere. The mutation is so uncommon. However, I think that for this mutation to take place, the genes of the parent must have been a carrier of something that could trigger this gene for the normal aging process to have a defect. Lastly, here is a few pictures of what some children look like with this disease. The second picture shows the symptoms and signs of this abnormal aging disorder.
Post #5
"Congratulations! You're having a baby!
Over the next nine months, millions of years of interaction with disease, parasites, plagues, ice age, heat waves, and countless other evolutionary pressures- not to mention a little romance- will come together in a stunningly complex interaction of genetic information, cellular reproduction, methyl marking, and the commingling of germlines to produce your little peanut." (page 192)
During the course of this year we have discussed cells, genetic information and DNA tremendously. I connecte this excerpt with the many activities that we did in class having to do with the cell stages of mitosis and meiosis. Not only did we devote an entie lab on this concept but also did a few computer activities to help with our understanding. When an egg cell from a woman and a sperm cell from a man come together, these cells will grow and divide and eventually produce a zygote which will grow into a fetus. The concept we focused on in class was sexual reproduction. "Mitosis and Meiosis describes the process by which the body prepares cells to participate in asexual and sexual reproduction to make an entire organism."(1) Mitosis is the reproduction of the autosomal cells such as the cheek or muscle cells. However, when only referring to mitosis, we are usually talking about asexual reproduction. This quote directly refers to a baby, which can only be produced by sexual reproduction. Meiosis is the production of sperm and egg cells. These cells are called gametes, or the "sex" cells of the body. Each of these cells must go through the rounds of division twice in order to obtain half the number of chromosomes. Because these cells only have half the number of chromosomes, 23 instead of 46, they are the haploid cells. Eventually they will combine with the opposite, sperm with egg or egg with sperm, to complete the 46 chromosomal set needed to make an organism. However, they must be haploid at first. These are the cells that pass on the genetic information to the offspring. Each of these cells contains chromosomes, like I stated before. The chromosomes are made up of strands of DNA, which is what is passed down to the offspring. DNA is in the shape of a double helix made of sugar bases, nucleotides and a phosphate backbone. "The nucleotides are grouped to form genes or alleles to pass on the information to the offspring. Here is a picture of what a DNA strand looks like with the nucleotides shown in different colors. In order to eventually get a baby, the cells must undergo 2 stages of meiosis. In meiosis one cell becomes four daughter cells. Each new gamete contains one half of the number of chromosomes of the parent cell. The stages of the cell cycle are interphase, prophase, metaphase, anaphase, telophase and cytokinesis. In prophase 1 of meiosis, the pairing of homologous chromosomes takes place. The resulting chromosome is called a tetrad which is made up of two chromatids from each chromosome. Crossing over may also happen at this point which is very important for evolution and the reason as to why every person looks different. Without crossing over we would look alot similar than we do now. Crossing over is essential in the sexual reproduction cycle. "During crossing over chromatids break and may be reattached to a different homologous chromosome." (2) Next is Metaphase 1. In Metaphase 1, the tetrads line up in the middle of the cell, on the "equator of the spindle." (2) Spindle fibers attach to the centromeres of the chromosome pairs. Next is Anaphase 1, which is when the tetrads separate and are drawn to opposite ends of the cell. Lastly is Telophase 1, depends on the species and some nuclear envelopes may appear. Also, sometimes the centrioles of some cells of different animals have division here. Next is the second round of division, meiosis 2. We go back to Prophase, and in Prophase 2, the nuclear envelopes that were formed in the Telophase 1 stage dissolve and the spindle fibers are once again here. Metaphase 2 is when the spindles move "chromosomes into the equatorial area and attaching to the opposite sides of the centromeres." (2) Next is Anaphase 2 where the centromeres split. The former chromatids which are now the chromosomes are also split and moved to opposite ends of the cell. Lastly, is Telophase 2 which is almost identical to the previous round of telophase however now we have four daughter cells. The chromosomes gather into the nuclei of each daughter cell and cytokinesis separates the cells. Each of the cells has a nucleus and half the number of chromosomes that the parent cell had. This process of cell division occurs and a blastocycst is formed and then eventually a zygote which will turn into a fetus. This process of meiosis and the two rounds of cell division after mitosis is needed for the genetic recombination of genes and making each person look differently and have different personality and physical characteristics. They will still have some of the same traits as the parents, obviously, however they will be their own person due to meiosis and crossing over. This excerpt relates to continuity and change which is a major theme in the biology course. Continutity and change is, "All species tend to maintain themselves from generation to generation using the same genetic code. However, there are genetic mechanisms that lead to change over time, or evolution."(3) All organisms and people have looked pretty much the same from generation to generation. Two eyes, one nose, one mouth, two arms, two legs and one body. Parents pass down their traits and characteristics however within each generation there is some change, no one is exactly the same, with the exception of identical twins. The same genes get passed down from each generations however variations occur because one partner is giving only half of their genetic information and the other partner is giving only half of their genetic information. A person needs both sets in order to live and function as a human being. We are seeing the result of variations and different combinations yet similarities in parents, children and grandparents. The genes are the same yet there is different combinations that create the differences. Also, during mitosis and meiosis mutations can occur that create changes in the chromosomes that the parent cells did not have. This could be something advantagous or something like the addition or deletion of a nucleotide base which could result in disease and abnormality within that person. Throughout the course of this year we have not only learned about mutations, diseases, advantages, disadvantages but also the idea of mitosis and meiosis. The quote says that all of the people and family that have come before you are apart of your genetic information. All of the diseases and bacteria that your line of family has come into contact with, will be in your genetic information somewhere. Through nine months of making the child inside of the womb of its mother it undergoes all of these cell processes and stages and is doing that to make itself its own person.
Survival of the Sickest
"Parasites hunt us for our iron; cancer cells thrive on our iron. Finding, controlling and using iron is the game of life. For bacteria, fungi, and protozoa, human blood and tissue are an iron gold mine. Add too much iron to the human system and you may just be loading up the buffet table." (Page 6)
Not only does the human body need iron to survive but all other living organisms need it too. Iron is an essential element in an organisms diet and occurs naturally in plant and animal life. Iron is needed for the well being of the organism as well as to provide energy. It is an element in the hemoglobin molecule which carries oxygen in red blood cells. However, as stated in the quote from the book, not only do humans and plants need iron but also, bacteria, fungi and protozoa. This relates directly to a topic of discussion that came up quite a bit in our studies this year, symbiotic relationships. There are seven different types of symbiotic relationships that occur between two individuals of different species. The first relationship is called cooperation where both individuals benefit but are independant of one another. An example of this would be with oxtail birds and gnus. "The gnu is covered in with tiny parasites that provide the bird with food and in return, the oxtail bird keeps the gnu free of parasites." (1) Mutualism is another form of a symbiotic relationship. In this case both individuals benefit but they are dependant upon eachother. An example of this could be the bacteria that resides in the human stomach. In other symbiotic relationships both individuals do not always benefit. In commensalism one benefits and the other in unaffected. However, in amensalism one individual is harmed while the other is unaffected. An example of this would be spanish moss that grows on trees. "Spanish moss grows on trees and chokes out virtually all light going to the tree. While the Spanish moss remains unaffected, the tree does not receive enough light to perform an adequate amount of photosynthesis to survive."(1) This relationship is much different than the one that is talked about in this excerpt. Parasitic symbiosis is when one individual is harmed and the other benefits. It could be as simply as a leech sucking the blood out of a human. These bacteria, parasites, fungi and protozoa mentioned all thrive off of iron, which essentially is human blood and tissue. In most cases this would not be a relationship that would benefit both the human and the bacteria. Connecting this idea of symbiosis to a major theme in biology would definitely have to be interdependance in nature.
Interdependance in nature basically states that every organism on earth depends on another one in nature to survive. Without plants and trees that produce oxygen into the air, humans would not be able to breathe. Without plants, animals that are not carnivores would go hungry. Everything depends on something else is order to survive. Even cancer cells use the iron in our blood to survive and reproduce. In this excerpt it seems as though iron is basically the most sought out nutrient and element in life. Because not only do we depend on it but every other organism depends on it too. A question to throw out there would be, what if iron did not exist? What would be composed in the make up of our red blood cells? As the excerpt goes on it says something interesting that also pertains to symbiotic relationships that do not benefit both individuals. "Add too much iron to the human system and you may just be loading up the buffet table." As everyone knows, a buffet table does not really benefit the table in any way. The people eating it are supplying their bodies with food and energy so only really affecting them. With too much iron, our bodies have become that table. The bacteria, fungi, protozoa and parasites are just feeding off of any and all iron they can get their mouths on. While looking at this excerpt one may not think these relationships could be harmful however the words, 'parasites' and 'cancer' are usually associated with harmful relationships. As previously mentioned parasitic relationships benefit one and harm the other. Cancer is a whole other topic however something that we discussed throughly in class. It is a rampant disease and cells divide and reproduce very quickly. If iron is a source used to enhance this process, then again loading our body up with iron is probably not a good idea. Iron is an essential element in the body's diet however too much of a good thing can be dangerous.
I think that this excerpt greatly connects with many themes that we have discussed in class throughout the year, especially interdependance in nature. We
discussed symbiotic relationships, positive and negative and how cancer cells will do anything to invade the body's organs and destroy them.I think that the level of difficulty of the reading is comparably low to what we have been reading all year however I would not really expect it to be any different. This book was written for people in general not just "science people."
Post 2
"On the other hand, as much as plants want animals to eat their fruit,they don't want animals to get much closer than that- when creatures start to nibble on their leaves or gnaw at their roots, things can get tricky. So plants have to be able to defend themselves. Just because they're generally immobile doesn't mean they're pushovers." (Page 78)
Just like the human body, plants have defense mechanisms to fight off diseases and unwanted materials that try to break through their cell walls. Whereas humans have nonspecfic and specfic defenese mechanisms, plants have passive and active defenses. A plant's passive defense would correlate with the job of the human skin. "This type of defense response is due to the presence of some structural components or some type of metabolites present in the body of the plant." (1) An example of this would be thorns,cuticle or wax which cannot be digested by predators to the such as fungi or bacteria. However, trees that have tough bark usually stop any bacteria from penetrating the surface and moving into the cells of the tree. The plant also contains secondary metabolites, which could be things such as alkaloids, tannins and phenols which are dangerous and toxic to insects and other pests. Because plants cannot run away from insects and animals that like to feed off of them, as stated in the excerpt they are "generally immobile," they need other things to keep them from being eaten and dying off. The other part of the plant's defense mechanisms is called active defense. Active defense is produced when the plant is exposed to a pathogen, it is a newly developed response inside the plant, it does not exist until the plant is exposed to some bacteria or pathogen. "The plant cell wall is one of the sites where the change due to the defense response can be observed. All changes that happen in the cell wall due to an infection are collectively known as wall apposition."(1) As a pathogen tries to enter the plant, the cell wall gets thicker in order to make the fungi or bacteria penetration impossible. Another active response mechanism is called HR, hypersensitive response. The metabolic activity of the cells around the infected site change, their respiration slows down and they start to accumulate toxic compounds. This creates a uncomfortable enviornment for the pathogen and essentially prevents the growth and spread of the pathogen throughout the plant and to more cells in the plant body. As these cells are exposed to the "new" bacteria they release chemicals called phytoalexins. "Phytoalexins are small molecular weight compounds produced when there is microbial attack or under conditions of stress, which are completely absent in healthy tissue." (1) Phytoalexins are related to memory B cells in the specfic defense mechanisms in the human body. The memory B cells can detect when their is a forgein invader and automatically stores that information. When the disease or pathogen comes in contact with the human again, these cells are released and find the invader and are able to fight off the disease quicker because of their memory of how to fight off the disease from earlier. The difference is that phytoalexins are not present in healthy tissue, memory B cells are however they are most useful at the site of an infection or bacteria that the body has seen before. The diagram below demonstrates the plant defense responses and what happens to the fungal pathogen as it enters the cell and where it goes from there. Other chemicals are shown that are not mentioned above however each of these goes into the process of defense that occurs within a plant when a pathogen tries to penetrate the cell wall.
There are also other things that plants do to help them survive because they cannot move. We discussed many things in class however one that stuck out in my mind was the regulation of the stomata and transpiration within the plant. Just because it is hot, humid and windy out does not mean a plant or tree can get up and find shade until the weather cools off. The regulation of the stomata opening during the day and closing during the night is something they plants do to defend themselves. The stomata are closed at night because photosynthesis can only take place with sunlight, during the day therefore if the stomata were to be open during the night, the plant would be transpiring and losing water for no reason. However, during the day if the plant is becoming dehydrated or if it starts losing alot of water, the stomata will close. This will help prevent the loss of too much water which can also be categorized as a defense mechanism. This excerpt can be connected to one of the major themes in biology which is regulation. Regulation is," Everything from cells to organisms to ecosystems is in a state of dynamic balance that must be controlled by positive or negative feedback mechanisms." (2) Everything in nature must be balanced. It could be the regulation of the stomata opening and closing or from "homeostatic control of cellular and body conditions."(2) The stomata is regulating the gas exchange in and out of the plant as well as keeping the levels of transpiration in tact.
Works Cited
Understanding the Defense Mechanisms in Plants. Hubpages Inc., 2010. Web. 2 June 2010. http://hubpages.com/hub/Understanding-the-Defense-Mechanisms-in-Plants. (1)
The Guiding Themes of Biology. 2007. Web. 2 June 2010. http://apbio12007.blogspot.com/2007/11/theme-6-regulation.html. (2)
Post #3
" 'Superbugs' spread fear far and wide. Rising deadly infections puzzle experts. Bacteria run wild, defying antibiotics. You've seen the headlines. They've probably frightened you. And it's true-just as we've been evolving to survive disease, all the organisms that cause disease have been evolving right along with us. You've seen how parasites have evolved very specialized abilities to navigate seemingly impossible challenges to survival- like travelling from a sheep to a snail to an ant in order to get to another sheep. And small organisms, because they multiply so rapidly and so frequently, sometimes cycling through hundreds of generations in just days, have one big evolutionary advantage over us- they evolve faster." (116-117)
The big question that has been circling the minds of scientists, researchers and the victims that the bacteria is infecting is, what are the bacteria doing to stay alive that we can't? The answer is right in this quote and I cannot agree more. These organisms are so small and so vicious that they will do anything to keep its "species" alive. It multiples and developes faster than humans can think. Because they are evolving faster they are also changing and mutating more and faster and figuring out ways to beat our strongest and highest levels of antibiotics. In today's society MRSA is a huge problem especially the staphylococcus aureus strain. The strain is a group of bacteria that can cause various disease as a result of infection from different tissues in the body. What is interesting is that the staph bacteria can be found on the skin of 25-30% of adults however it will not do any harm until the skin is broken and an infection breaks out. MRSA is today's "superbug." Not only is it getting harder and harder to treat but because the survival rate of very severe MRSA infections is so low, the disease is surviving and moving on to other victims. In class we not only talked about MRSA and did a lab demonstrating how the bacteria in the noses of some classmates could be resistant to some of the highest antibiotics, such as vancomysin and lyncomysin. I can also connect this quote with Darwin's Theory of Natural Selection. "As many more individuals of each species are born than can possibly survive; and as, consequently, there is a frequently recurring struggle for existence, it follows that any being, if it vary however slightly in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance of surviving, and thus be naturally selected. From the strong principle of inheritance, any selected variety will tend to propagate its new and modified form."(1) This is basically stating that organisms will evolve to better themselves and if they don't their species will die off. Organisms that have certain traits that make them weak, they should be cut off from the world according to the natural selection theory. This theory can connect with the superbug craze because the people that do not aquire this disease or who have some mutation in their bodies that prevent them from dying from diseases, like MRSA, they are the organisms that will move on. They are the organisms that will pass their traits on and then generations after them can beat and survive the superbug. According to the natural selection theory, the people who do contract this "bug" are meant to die because they cannot survive and live through the natural bacteria that is passing through the generations of people today. This image is showing a magnified view of the staph aureus bacteria.
http://en.wikipedia.org/wiki/Charles_Darwin#Inception_of_Darwin.27s_evolutionary_theory (1)
http://www.allaboutscience.org/what-is-evolution-faq.htm (2)
Post #4
"In April 2003, researchers announced that they had isolated the genetic mutation that causes progeria. The mutation occurs in a gene that is responsible for the production of a protein called lamin A. Normally,lamin A provides structural supports for the nuclear membrane, the package that houses your genes at the core of every cell. Lamin A is like the rods that hold up a tent- the nuclear membrane is organized around it and supported by it. In people who ave progeria, lamin A is defective and cells deteriorate much more rapidly." (page 184)
All genes are responsible for different traits and characteristics of the body. A gene resides at a specific location on the chromosome which is commonly called the gene locus. The place in which a gene is located determines what trait or characteristic it expresses. When looking at this quote, it talks about progeria which is a very rare aging disorder. People usually die in their teens with this disorder and no one has said to live past 30. This is because by the time the individual that posseses this disorder is one and a half years old, their hair starts to fall out and their skin starts to wrinkle. In the book, Survival of the Sickest, it talks about a boy who is 12 years old however has symptoms of one of the oldest people in America. He takes pills to thin his blood, his arteries are hardened and he has arthritis. Usually people with this disorder die in their teens from a heart attack or a stroke. Not only is this the result of a genetic mutation, but the gene on the locus of the chromosome that maintains the steady aging process, would have to be defected in some way. A mutation is, "a permanent change in the DNA sequences that makes up a gene. Mutations range size from a single DNA building block to a large segment of a chromosome."(1) Gene mutations can occur in two different ways, being inherited from a parent or acquiring this mutation during a person's lifetime.Mutations that are passed down from the parents to the children are called hereditary mutations. It is present in every cell throughout the person's body throughout their lifetime. There are mutations that only in occur in the sperm or eggs cells, which are called De novo mutations. These mutations help people understand why a child has a certain disorder however their is no history of that disorder in the child's parents or family. Lastly, there is something called acquired mutations that occur in the DNA of individual cells throughout a person's life. These mutations can be the result of environmental factors such as ultraviolet radiation from the sun. It is important to note however, that these mutations cannot be passed down. The genetic disorder of progeria would be classified, I believe, in the De novo mutation category. Neither parent would have this disease because if they did, they would not live long enough to have a child. Also, this disorder is so rare, only 1 child gets this disease in 8 million births. It would not be possible to have a family history of this because it is not that common. There must be some kind of mutation in the sperm and/or the egg once fertilization takes place. This excerpt connects to what we have learned this year in class because we have specifically talked about chromosomes, genes and traits that will or will not be expressed because of certain factors. We have also discussed mutations and why they occur and what results from a mutations. When I read this excerpt I immediately thought of the karyotype activity where each chromosome was visible and each student was asked to pick out the mutations or the defects and figure out the disease in which the person had. Here is a picture of a karyotype for a person with the progeria disease.
Also, like it says in the quote, this disease is caused by a mutation in the LMNA gene. "The LMNA gene produces the Lamin A protein, which is the structural scaffolding that holds the nucleus together. Researchers now believe that the defective Lamin A protein makes the nucleus unstable. That cellular instability appears to lead to the process of premature aging in Progeria."(2) By just one small change in the certain gene at a certain point along the chromosome, it could drastically affect the future life of that individual. The theme that this connects to is genetics. "Genetics is the branch of biology that deals with heredity, especially the mechanisms of hereditary transmission and the variation of inherited characteristics among similar or related organisms." (3) Personally, I believe that everything must come from someone or somewhere. These mutations must be triggered by something in the parent cell even if the parent cell does not possess the gene or the defect that will cause certain diseases. Everything is based off of genetics, the way we look, the way we talk, and the way we act. Just because there are two parents with brown hair that have a child with blonde hair, does not mean this gene for blonde hair popped up out of nowhere. The topic of recessive and dominant alleles and genes will then come into play. However, according to the research done on the aging disease, progeria, it does come from nowhere. The mutation is so uncommon. However, I think that for this mutation to take place, the genes of the parent must have been a carrier of something that could trigger this gene for the normal aging process to have a defect. Lastly, here is a few pictures of what some children look like with this disease. The second picture shows the symptoms and signs of this abnormal aging disorder.
http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/genemutation (1)
(2) [[http://www.progeriaresearch.org/about_progeria.html (2|http://www.progeriaresearch.org/about_progeria.html ]]
http://www.answers.com/topic/genetics (3)
Post #5
"Congratulations! You're having a baby!
Over the next nine months, millions of years of interaction with disease, parasites, plagues, ice age, heat waves, and countless other evolutionary pressures- not to mention a little romance- will come together in a stunningly complex interaction of genetic information, cellular reproduction, methyl marking, and the commingling of germlines to produce your little peanut." (page 192)
During the course of this year we have discussed cells, genetic information and DNA tremendously. I connecte this excerpt with the many activities that we did in class having to do with the cell stages of mitosis and meiosis. Not only did we devote an entie lab on this concept but also did a few computer activities to help with our understanding. When an egg cell from a woman and a sperm cell from a man come together, these cells will grow and divide and eventually produce a zygote which will grow into a fetus. The concept we focused on in class was sexual reproduction. "Mitosis and Meiosis describes the process by which the body prepares cells to participate in asexual and sexual reproduction to make an entire organism."(1) Mitosis is the reproduction of the autosomal cells such as the cheek or muscle cells. However, when only referring to mitosis, we are usually talking about asexual reproduction. This quote directly refers to a baby, which can only be produced by sexual reproduction. Meiosis is the production of sperm and egg cells. These cells are called gametes, or the "sex" cells of the body. Each of these cells must go through the rounds of division twice in order to obtain half the number of chromosomes. Because these cells only have half the number of chromosomes, 23 instead of 46, they are the haploid cells. Eventually they will combine with the opposite, sperm with egg or egg with sperm, to complete the 46 chromosomal set needed to make an organism. However, they must be haploid at first. These are the cells that pass on the genetic information to the offspring. Each of these cells contains chromosomes, like I stated before. The chromosomes are made up of strands of DNA, which is what is passed down to the offspring. DNA is in the shape of a double helix made of sugar bases, nucleotides and a phosphate backbone. "The nucleotides are grouped to form genes or alleles to pass on the information to the offspring. Here is a picture of what a DNA strand looks like with the nucleotides shown in different colors.
http://www.schools.utah.gov/curr/science/sciber00/7th/genetics/sciber/compare.htm (1)
http://www.emc.maricopa.edu/faculty/farabee/biobk/biobookmeiosis.html (2)
http://apbio12007.blogspot.com/2007/11/theme-4-continuity-change.html (3)